Immunology is a branch of biomedical science that investigates the immune system and its response to foreign substances, infections, and diseases. It encompasses the study of immune cells, antibodies, cytokines, and various immune processes. Immunologists aim to understand how the immune system protects the body from harmful pathogens and develops therapies to combat immunological disorders. This book introduces the fundamental principles and experimental methods used in the study of the immune system and its response to pathogens.